DECREASING QUANTITY OF ORGANIC CARBON IN CAUSTIC ALUMINATE SOLUTION AND INCREASING SOLUBILITY OF BAUXITE IN CAUSTIC ALUMINATE SOLUTION

摘要

PURPOSE: To make it possible to decrease an org. carbon content by heating bauxite for a specific time at a specific temp., without converting gibbsite to alumina insoluble in caustic aluminate. ;CONSTITUTION: The bauxite is thermally pretreated before introduction to a Bayer process to decrease the amt. of the org. substances in the caustic aluminate and to convert the existing gibbsite to a form having higher solubility. The heat treatment is executed by heating for about 10 to 120 minutes, more preferably for 20 to 30 minutes within a range of 300 to 400°C, most adequately at 360°C. As a result, the amt. of the org. carbon of the bauxite may be decreased down to about 70% and the sodium oxalate forming capacity is lowered down to 1/10. The gibbsite is converted to the alumina species which dissolve at least more by 25% than the gibbsite into the caustic alkali soln.;COPYRIGHT: (C)1990,JPO